During the completion of oil and gas wells, it is frequently necessary to anchor well equipment, typically a production tubing or well packer, within a well conduit such as a well casing or liner. A large number of anchoring devices have been developed and are employed for this purpose. Usually, the anchoring means employed to anchor the well equipment in place is lowered down through a well conduit to the desired subsurface location and then suitably manipulated or actuated from the surface to cause gripping means, or "slips", and sometimes sealing means, to move radially into engagement with the surrounding well conduit. This operation, referred to usually as "setting" the equipment may be accomplished by physical movement of the tubing string from which the equipment is suspended, in which case, the anchoring and/or sealing means of the equipment is "mechanically set". Such anchoring or sealing means may also be radially extended by the application of hydraulic pressure to an expansion chamber contained within the equipment. In the latter case, the anchoring and/or sealing means is considered to be "hydraulically set". Various other means, including electrically operated setting tools and explosive devices have been employed to set anchoring and/or sealing devices at subsurface locations within a well bore.
The anchoring mechanism in a well packer as well as that in a liner hanger and other equipment must frequently support large structural loads. This fact, coupled with the need to remotely operate the anchoring mechanism from the well surface, make it important to employ devices which may be reliably set and which, when set, can remain set even though exposed to substantial weight and pressure induced forces. Retrievably anchored devices must have all of the foregoing characteristics and in addition, be readily released from their set position when their retrieval is desired.
The large forces which are acting upon these anchoring devices have traditionally required the use of relatively large, heavy components and wedge-type locks. Unless sufficiently heavy, the components may be crushed or distorted by the wedge-type lock designs which are commonly employed. The large size of the components has necessarily limited the size of the central flow passage usually provided through the anchoring device. This passage, which is used to flow the oil or gas being produced, is desirably maintained as large as possible to more efficiently flow the subsurface effluent and also to facilitate movement through the conduit of wireline tools and other equipment which is frequently required in either completing or working over the well.